Class Asteroidea• Pedicellariae • Tiny pincher-like organs

on the aboral side keep the surface clean

• Most sea stars are predators of bivalves, snails, or other attached or slow moving animals

Class Ophiuroidea• Includes: Brittle Stars• Legs proportionally

longer and thinner than sea stars

• Allows for better movement

• Organs in central disc• Tube feet lack

suckers

Class Ophiuroidea

• Eat organic matter and small animals they find on the bottom

Class Echinoidea

• Includes: Sea Urchins & Sand Dollars

• Body structure forms a round, rigid body with movable spines and pedicellariae

• Locomotion achieved by movable spines

Class Echinoidea• Body plan of sea stars

repeated by moving arms upward and connecting them at the tips

• Mouth is on the bottom, anus on the top

• Spines: sharp, hollow and sometime contain venom

Plates:

• 10 plates• Alternating abulacral

(have openings for tube feet) and interambulacral (bumps for spines)

Class Echinoidea

• The mouth has an intricate system of jaws and muscles called Aristotle’s Lantern

• Used to bite off algae and other bits of food from the bottom

Class Echinoidea

• Heart Urchins and Sand Dollars are adapted for the soft bottom of the ocean

• Flat bodies and short spines

Class Holothuroidea

• Sea Cucumbers• Similar body plan to

a sea urchin, just stretched out from mouth to anus

• Lies on sides, oral and aboral surfaces are at the ends

Class Holothuroidea• Most have five rows of

tube foot that run mouth to anus

• Some excrete toxic substance as defense mechanism

• Some expulse gut and other internal organs out of the mouth or anus, called evisceration

• Believe that they grow the organs back